ci: introduce action implementing feature request prioritization process (#41975)

Enable a GitHub action that implements our new feature request
[process](ce8e011a9f/docs/GITHUB_PROCESS.md (feature-request-process)).

As a prerequisite, we need to create the following labels:
- `in backlog`
- `votes required`
- `under consideration`
- `insufficient votes`

The bot will also use the existing `feature` label to identify feature
requests.

With its current configuration, we need to kick the process off
manually. We currently also have a limit, meaning the bot will process
only 50 feature requests before it exits. Additionally, now the bot will
not close issues, it'll just comment on them and if they have an
insufficient number of votes, the bot will label them with `insufficient
votes`.

On the next iteration, we can:
- Expand the limit from 50 to infinity (removing the option from the
yml file)
- Set a cron configuration to kick off the bot automatically
- Enable autoclose by setting the `close-when-no-sufficient-votes` to
`true`

PR Close #41975

.github/workflows/feature-requests.yml

@@ -0,0 +1,13 @@
+name: Feature request triage bot
+
+on: [workflow_dispatch]
+
+jobs:
+  feature_triage:
+    if: github.repository == 'angular/angular'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: angular/dev-infra/github-actions/feature-request@ab1b92098e112b846e54a021458662b529276208
+        with:
+          token: ${{ secrets.FEATURE_REQUEST_BOT_TOKEN }}
+          limit: 50